Shampoo compositions for cleaning the hair which also contain anti-dandruff agents are well known. Among the preferred types of anti-dandruff agents are particulate, crystalline anti-dandruff agents, such as sulfur, selenium disulfide, and heavy metal salts of pyridinethione. In order for these types of shampoos to be effective and to provide a consistent level of performance, without requiring vigorous shaking of the package in which they are contained, it is conventional practice to suspend them in the composition with the aid of a suspending agent. Since shampoos are likely to remain on shelves or in storage for long periods of time, it is important for the suspending agents to keep the particulate anti-dandruff agents well suspended for relatively long periods of time. The suspending agents which have become preferred for suspension of particulate anti-dandruff agents are those which form a crystalline network in the shampoo when the shampoo is stationary, but which allow the composition to readily flow when shear is applied, such as when a user pours it out of a bottle. Examples of such suspending agents include ethylene glycol distearate and N, N- di- (hydrogenated tallow) amido benzoic acid. Crystalline suspending agents are currently the preferred method for suspending particulate anti-dandruff agents in the marketplace.
Other suspending agents which are known include hydrophilic polymeric thickening agents such as cellulosic gums and acrylic acid/acrylate polymers, the latter of which are commonly referred to as carbomers. Although these materials are effective for suspending particulate matter, at higher levels they tend to impart an undesirable, slimy feel.
Just as important as suspending the anti-dandruff agent , the suspending agent must also allow the anti-dandruff agent to deposit on the scalp during use. If too little anti-dandruff agent deposits, it will be unable to provide good anti-dandruff efficacy. The polymeric suspending agents are believed to be less efficient than the crystalline suspending agents for deposition of active ingredients on the scalp and hair.
Another drawback of crystalline suspending agent is that they require costly heating and cooling steps in the manufacture of the compositions in order to make high quality stable suspensions.
Another important parameter in the formulation of anti-dandruff shampoos is lathering. The consuming public often associates high lathering with effective cleaning, and typically prefers high lathering shampoos to low lathering shampoos from an aesthetic standpoint. Unfortunately, crystalline suspending agents tend to adversely affect lathering performance.
It is also known to prepare antimicrobial compositions utilizing finely powdered polyvalent metal salts of 2-mercaptopyridine-N-oxide, e.g., zinc pyridinethione. See, for example, U.S. Pat. No. 4,832,950 (Takaya et al., issued May 23, 1989) and U.S. Pat. No. 4,670,430 (Inamura et al., issued Jun. 2, 1987). In these compositions, very small average particle size of less than 0.2 microns, are said to provide improved dispersion stability without the use of polymeric suspending agents or other means to suspend larger particles. Compared to such prior compositions, the compositions of Imamura et al. are said to provide improved adsorbability. Takaya et al. teaches further suspension stability of the small particles of Imamura et al. via the use of a specific dispersent selected from the group consisting of: (A) polyglycol/polyamine polyglycol/polyamine/alkylamine or alkyleneamine condensation polymers; (B) water soluble polymers selected from the group consisting of hydroxyalkylcelluloses and partly quaternized products thereof, and at least one nonionic surfactant; and (C) at least one cationic polymer compound and at least one inorganic salt.
Although the above compositions avoid the use of conventional suspending agents, deposition efficiency of the particulate metal salts remains impaired due to the extremely small size of these particles. Because of their small size, a proportion of them would tend to remain dispersed in solution rather than deposit on the scalp, skin, or hair.
Thus, it would be desirable to provide liquid topical composition with a stable dispersed anti-dandruff agent, which utilized larger particles than those specified in the above patents, but which also did not require the use of conventional suspending agents such as crystalline suspending agents or polymers added for thickening purposes.
It is an object of this invention to provide anti-dandruff shampoos containing particulate anti-dandruff agents that are suspended without the need for crystalline suspending agents, but which still retain efficient deposition of the anti-dandruff agent on the hair or scalp. It is another object of this invention to provide anti-dandruff shampoos containing particulate anti-dandruff agents that are suspended without the need for hydrophilic polymeric thickening agents, but which still retain efficient deposition of the anti-dandruff agent on the hair or scalp.
It is another object of this invention to provide such compositions, as set forth above, which have good, non-slimy feel. It is yet another object of this invention to provide compositions as set forth above which have improved deposition efficiency on the skin, scalp and/or hair, relative to conventional suspending agents for particulate matter in liquid topical compositions. It is still another object of this invention to provide compositions, as set forth above, which can be made without the need for costly heating and cooling steps, as conventionally utilized when crystalline suspending agents are employed.
It is yet another object of this invention to provide a process for making anti-dandruff shampoos meeting the above objects.
These and other benefits as may be apparent or otherwise realized can be obtained according to the present invention, which is described below.
Unless otherwise indicated, all percentages are calculated by weight of the total composition, and all ratios are calculated on a weight basis. Unless otherwise indicated, ingredients are based on the active level and, therefore do not include carriers or by-products that may be included in commercially available materials. The present invention may comprise, consist of, or consist essentially of any of the essential and various optional and/or preferred ingredients and elements described herein.